howto:column_spanning [SwingWiki]

Column spanning with JTable

In an equaly distributed table, a single cell is an intersection of a single row and a single column. However, for design purposes, it is often convenient to use group table column headers (above a sequence of cells), and sometimes several vertical cells are containing the same data, so they can be merged into one single large cell. Word processing and spreadsheet software usually uses terms like “merged cells” for joined cells, and in HTML terminology, merged cells are often denoted by column-spanning and row-spanning. We will use HTML terminology here, since it is more precise and takes into account a difference betweek horizontal (column) and vertical (row) merging.